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Poly(acrylic acid)와 Poly(ethylene oxide)의 착체형성에 대한 용매와 온도의 영향
이장우,안희준 釜山大學校生産技術硏究所 1998 生産技術硏究所論文集 Vol.55 No.-
수소 결합을 통한 고분자 착체 형성에 있어서 용매의 종류와 온도의 영향을 조사하기 위하여 poly(acrylic acid)(PAA)와 poly(ethylene oxide)(PEO) 착세계에 대하여 용매는 순수 물 및 물-메탄올(30 wt%) 혼합 용매의 두 종류를 선택하여 이들 용매에서의 착체 형성거동의 차이를 모세관 점도계, 전위차계 및 UV 분광기를 사용하여 여러온도에서 조사하였다. 환원점도의 측정을 통하여 물에 메탄올을 첨가하면 최대 착체 형성점에 해당하는 반복단위 몰비가 [PEO]/[PAA]=1.2:1 부근에서 1.5:1로 이동함이 밝혀졌다. UV 측정에서 용액의 흡광도가 일정하게 되는 소위 "isobestic"점으로부터 이탈 현상은 착체 형성에 대한 용매효과를 다시 입증해 주었다. 그리고 여러 온도에서 pH 측정을 통하여 추정한 열역학적 성질들의 변화로부터 30℃이상의 고온에서는 혼합용매에서의 착체 형성 거동이 순수 용매의 경우에 비하여 더욱 불리해졌다. 이것은 물에서는 수소결합은 물론 소수성 상호작용도 착체 안정화에 큰 기여를 하나, 물-메탄올에서는 주로 수소결합만이 착체 형성에 관여하고 있기 때문이라 생각된다. To investigate the effects of solvent type and temperature on the interpolymer complexation via hydrogen bonding, a study was made on the complex system of poly(acrylic acid(PAA) and poly(ethylene oxide)(PEO) in two kinds of solvent systems, pure water and water-MeOH(30 wt%) mixed solvent, at various temperatures using the Ubbleohde viscometer, pH-meter and UV spectrophotometer. The repeating unit mole ratio at the most optimum complexation as confirmed by the reduced viscosity measurement was shifted from [PEO]/[PAA] 1.2:1 to 1.5:1 by the addition of methanol to water. From the UV measurement, the deviation from the "isobestic point" (where the absorbance of the solution remains constant) has presente another evidence for the solvent effect on complexation. In addition, the analysis of the changes in thermodynamic properties upon complexation as estimate from pH measurement at several temperatures reveals that the complex formation in mixed solvent became more unfavorable compared to that in pure solvent at high temperatures above 30℃. This could be explained by considering that in water the hydrophobic interaction as well as the hydrogen bonding may greatly contribute to the stabilization of the polymer complex formed, while in water-methanol the main stabilizing force would be the hydrogen bonding alone.
[논문]여러 용매계에서 Poly(vinylidene fluoride) 의 물리적 젤화에 대한 동력학 및 열역학 연구
백승태,김봉수,이장우 釜山大學校生産技術硏究所 2006 生産技術硏究所論文集 Vol.65 No.-
Poly (vinylidene fluoride) (PVDF) 물리 젤은 각 기 다른 조 건 에 서 v-butyrolactone, cyclohexanone, propylene carbonate와 같은 다양한 유기용매에서 형성된다. 첼 녹는점은 시차주사열량계로 측정하였고 젤화 시간은 시험관 틸팅방법을 통해 측정하였다. 임계 젤 농도는 PVDF의 농도와 젤화 속도로 결정되어진다. 본 연구에서는 젤화 속도는 임계 농도를 얻기 위해 구하였다. 젤화 속도는 온도에 높게 의존한다; 젤화 속도는 젤화 시간의 역수로 분석 가능하며/ 젤화는 낮은 농도에서 투명한 젤이 형성되어지는 것과 젤 형성을 위한 엔탈피 변화가 적기 때문에 낮은농도에서 액-액 상분리에 의해 일어난다. 실온에서 천천히 건조시킨 젤 필름을 주사전자현미경으로 관측하였고 젤 필름에서 많은 구정과 연결 분자 들을 관찰하였다.
Jang, Chun-Hag,Kim, Hyun-Don,Lee, Jang-Oo Korean Chemical Society 1994 Bulletin of the Korean Chemical Society Vol.15 No.5
The non-Newtonian viscosities (the specific or intrinsic viscosities) of poly(L-proline) (PLP, $M_v$=19,000 and 32,000) in various mixed-solvent systems like water-propanol and acetic acid-propanol of varying compositions were measured during the reverse mutarotation (Form II ${\rightarrow}$Form I) by the application of external pressure (up to 4.5 psi). The non-Newtonian viscosity effect was found to be larger in acetic acid-propanol system than in water-propanol system and to somewhat decrease during the reverse mutarotation at a given solvent system. The non-Newtonian viscosity behavior of PLP in aqueous salt ($CaCl_2$) solution was also studied, from which it was found that the degree of the non-Newtonian effect decreased with increasing salt concentration, and increased with increasing PLP molecular weight. These findings could be explained in terms of conformational changes of PLP in solution (like the helix-helix or helix-coil transition) involved.
Oo, May Moe,Yoon, Ha-Yeon,Jang, Hyun A,Oh, Sang-Keun The Korean Society of Plant Pathology 2018 Plant Pathology Journal Vol.34 No.6
Bitter rot caused by Colletotrichum species is a common fruit rotting disease of apple and one of the economically important disease in worldwide. In 2015 and 2016, distinct symptoms of bitter rot disease were observed in apple orchards in five regions of South Korea. In the present study, infected apples from these regions were utilized to obtain eighteen isolates of Colletotrichum spp. These isolates were identified and characterized according to their morphological characteristics and nucleotide sequence data of internal transcribed spacer regions and glyceraldehyde-3-phosphate-dehydrogenase. Molecular analyses suggested that the isolates of Colletotrichum causing the bitter rot disease in South Korea belong to 4 species: C. siamense; C. fructicola; C. fioriniae and C. nymphaeae. C. siamense and C. fructicola belonged to Musae Clade of C. gloeosporioides complex species while C. fioriniae and C. nymphaeae belonged to the Clade 3 and Clade 2 of C. acutatum complex species, respectively. Additionally, we also found that the isolates of C. gloeosporioides species-complex were more aggressive than those in the C. acutatum species complex via pathogenicity tests. Taken together, our results suggest that accurate identification of Colletotrichum spp. within each species complex is required for management of bitter rot disease on apple fruit in South Korea.